PrincipalProps类 参考

Public 成员函数
boolean	HasSymmetryAxis ()
boolean	HasSymmetryAxisByTol (double aTol)
boolean	HasSymmetryPoint ()
boolean	HasSymmetryPointByTol (double aTol)
GXYZ	Moments ()
GVec	FirstAxisOfInertia ()
GVec	SecondAxisOfInertia ()
GVec	ThirdAxisOfInertia ()
GXYZ	RadiusOfGyration ()

详细描述

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获取几何对象的主属性

成员函数说明

FirstAxisOfInertia()

GVec PrincipalProps.FirstAxisOfInertia

(

)

returns the first axis of inertia.
if the system has a point of symmetry there is an infinity of
solutions. It is not possible to defines the three axis of
inertia.

HasSymmetryAxis()

boolean PrincipalProps.HasSymmetryAxis

(

)

returns true if the geometric system has an axis of symmetry.
For comparing moments relative tolerance 1.e-10 is used.
Usually it is enough for objects, restricted by faces with
analytical geometry.

HasSymmetryAxisByTol()

boolean PrincipalProps.HasSymmetryAxisByTol

(

double

aTol

)

returns true if the geometric system has an axis of symmetry.

参数

aTol	is relative tolerance for checking equality of moments If aTol == 0, relative tolerance is ~ 1.e-16 (Epsilon(I))

HasSymmetryPoint()

boolean PrincipalProps.HasSymmetryPoint

(

)

returns true if the geometric system has a point of symmetry.
For comparing moments relative tolerance 1.e-10 is used.
Usually it is enough for objects, restricted by faces with
analytical geometry.

HasSymmetryPointByTol()

boolean PrincipalProps.HasSymmetryPointByTol

(

double

aTol

)

returns true if the geometric system has a point of symmetry.

参数

aTol	is relative tolerance for checking equality of moments If aTol == 0, relative tolerance is ~ 1.e-16 (Epsilon(I))

Moments()

GXYZ PrincipalProps.Moments

(

)

Return the principal moments of inertia in the current system.
Notes :

• If the current system has an axis of symmetry, two
  of the three values Ixx, Iyy and Izz are equal. They
  indicate which eigen vectors define an infinity of
  axes of principal inertia.
  
• If the current system has a center of symmetry, Ixx,
  Iyy and Izz are equal.

RadiusOfGyration()

GXYZ PrincipalProps.RadiusOfGyration

(

)

Returns the principal radii of gyration Rxx, Ryy
and Rzz are the radii of gyration of the current
system about its three principal axes of inertia.
Note that:

• If the current system has an axis of symmetry,
  two of the three values Rxx, Ryy and Rzz are equal.
  
• If the current system has a center of symmetry,
  Rxx, Ryy and Rzz are equal.

SecondAxisOfInertia()

GVec PrincipalProps.SecondAxisOfInertia

(

)

returns the second axis of inertia.
if the system has a point of symmetry or an axis of symmetry the
second and the third axis of symmetry are undefined.

ThirdAxisOfInertia()

GVec PrincipalProps.ThirdAxisOfInertia

(

)

returns the third axis of inertia.
This and the above functions return the first, second or third eigen vector of the
matrix of inertia of the current system.
The first, second and third principal axis of inertia
pass through the center of mass of the current
system. They are respectively parallel to these three eigen vectors.
Note that:

• If the current system has an axis of symmetry, any
  axis is an axis of principal inertia if it passes
  through the center of mass of the system, and runs
  parallel to a linear combination of the two eigen
  vectors of the matrix of inertia, corresponding to the
  two eigen values which are equal. If the current
  system has a center of symmetry, any axis passing
  through the center of mass of the system is an axis
  of principal inertia. Use the functions
  HasSymmetryAxis and HasSymmetryPoint to
  check these particular cases, where the returned
  eigen vectors define an infinity of principal axis of inertia.
  
• The Moments function can be used to know which
  of the three eigen vectors corresponds to the two
  eigen values which are equal.
  
  if the system has a point of symmetry or an axis of symmetry the
  second and the third axis of symmetry are undefined.